Gear type pump with pressure loaded bushing and wear insert element



2,654,325 ESSURE LOADED INSERT 11, 19

Oct 1953 R. J. MINSHALL GEAR TYPE PUMP WITH PR BUSHING AND WEAR ELEMENTFiled Aug. 50

insfiall fnuenZ or" Patented Oct. 6, 1953 GEAR TYPE PUMP WITH PRESSURELOADED BUSHING AND WEAR INSERT ELEMENT Robert J. Minshall, ShakerHeights, Ohio, in signor to Borg-Warner Corporation, Chicago, 111., acorporation of Illinois Application August 11, 1950, Serial No. 178,939

This invention relates to a pressure loaded pump and more particularlyto a bushing con-, struction for a pressure loaded type, intermeshingear pump.

In a pressure loaded type gear pump one set of bushings are made axiallymovable in response to discharge pressure, a part of the dischargepressure being applied to the rear or motive surfaces of the axiallyadjustable bushings to urge the forward surfaces of these-bushings intosealing engagement with the adjacent side faces of their associatedgears. As disclosed in U. S. Patent No. 2,420,622 to- Roth et al., bycarefully selecting the relative areas of the forward surfaces of thebushings and of the rear motive 4 Claims. (01. 103-125;)

2 the adjacent side surface of the associated pumping gear, the innerdiameter of the annular plate being slightly greater than the outerdiameter surfaces of the bushings, it is possible to con- I drawingswherein:

of the associated pumping gear journal. In this manner, there isprovided an annular chamber or relief recess which corresponds to thegroove ordinarily provided in the forward surface of each of thepressure loadable bushings.

one set of axially movable bushings construct- ,,,.;edin accordance withthis invention; and

higher effective pressure in the direction of establishing the seal thanin the direction tending to open the seal. e

As disclosed in the aforementioned patent, in order to control theeffective areas subjected to discharge pressure at the forward surfacesof the axially movable bushings, one practice is to form a groove orrecess, which is vented to a zone of low pressure, either in the forwardor gear side face engaging surface of the bushing or in the adjacentsurface of the pumping gear, the groove in either case being locatedradially inwardly of the pumping gear teeth. Because the dimensions ofthis groove are critical, since the degree of overbalance is directlycontrolled by the area of the groove, the machining operation involvedin forming the groove is one which must be carried outwith the greatestprecision. This, of course, contributes materially to the cost of thebushings.

An object of the present invention is to provide a new and improvedbushing construction for a pressure loaded type pump which will reducematerially the cost of the bushings.

A further object of the present invention is Fig. 2 is a transverse,sectional view taken substantially along the line 2-2 of Fig. 1 andshowing to advantage the relative dimensions of the annular inserts andthe associated bushpumping gears l0 and II which are rotatably Yjournalled therein. The chambers 8 and 9 are suitably formed to receiveand support on either side of the pumping gears in and H hearing orbushing means l2, l3 and I 4, l5, respectively. These bushing assembliesare radially flanged at their ends adjacent the gear side surfaces whiletheir tubularbody portions or barrels extend in opposite directions awayfrom the pump gears, the body portions providing jourto provide abushing construction having increased durability for a pressure loadedtype Dump.

A still further object of the present invention is to provide a bushingconstruction wherein the area or the relief recess may be readily variedto make the pump easily adaptable to different operating conditions.

In accordance with one embodiment of this invention as applied to apressure loaded type, intermeshing gear pump such as that .disclosed inthe aforementioned patent, each of the axially movable, pressureloadable bushings is formed so that the forward surface is substantiallyfiat and an annular plate or insert is provided which is positionedbetween this forward surface and nal support for the pump gear shaftsIlla and Ila. Low pressure liquid is introduced into the pump housing atinlet [8 and high pressure liquid is delivered from the outlet I9, theinlet and outlet passages communicating, respectively, with the inletand discharge sides of the intermeshing pumping gears.

In the embodiment illustrated, the upper pumping gear I0 is the drivinggear and, accordingly, the left end'portion of gear journal lfla isextended to the left to provide an externally splined couplingtermination 20. The coupling termination 20 is received in the recessedright end of an internally splined coupling and packing member 2|,having a radially extending flange 22 engaging a ring 23, the oppositeside of which ring presses against a flexible ring seal 24 retainedagainst a similarly recessed portion of an annular retainer plate 25mounted on and secured to the left side of housing section 5. Coupling2| terminates at its outer end in an internally splined connector recess26 adapted to be engaged in driving relation with an auxiliary powershaft, such asshaftZ'I, of an aircraft engine or other drivingmechanism..

Compression spring 28 received in axially extending chamber 29 formed inthe coupling termination 20 at the left end of gear shaft la tends tourge the coupling member 21 to the left, thus eliminating initial endplay and effecting an initial sealed engagement of flange 22, ring 23and flexible seal 24. In the operation of this pump, the intermediateliquid pressure communicated to the seal, as explained in detail in theabove-referred-to Patent No. 21420522 is effective to cause theoperation of the seal assembly.

It will be noted that the flanged bushing assemblies l3 and I5 disposed,respectviely, on the right sides of gears l0 and H are fitted into thebores 8 and 9 with sufficient end clearance to per-' mit slight, axialmovement of the bushings with respect to the bores. In the operation ofthis pump, discharge pressure generated by the intermeshing gears iscommunicated from the outlet or discharge side thereof to the annularpressure loading chambers defined by the rear flanged surfaces l3a andl5a of the bushing assemblies l3 and IS, the adjacent walls of thehousing section 6 and the barrel portions of the bushing assembliesthrough an axially extending passage 30 formed between the peripheriesof the flanged portions of the bushings l3 and [5 on the discharge sideof the pump at the point of convergence of the bushing assemblies. Thepassage 30 extends from the discharge side of the gears to the right, asviewed in Fig. l, to the intercommunicating portions of the pressureloading chambers at their point of juncture. In the operation of thepump discharge pressure is effective to move the bushing assemblies intosealing relation with the associated gear side faces.

Initia loading pressure is provided by helically coiled springs 3| and32, respectively. the spring 3| being associated with the upper bushingl3, and the spring 32 being associated with the lower bushing l5. Moreparticularly, spring 3| has its right portion disposed in a cylindricalrecess 33 formed in the cover member 6, and its left end bears againstan annular disc 34 disposed in the right end of bore 8 and engaging atits left side of the right end of bushing l3. A similar arrangement isprovided for the spring 32, which is disposed in a recess 35 and bearsagainst annular plate 33.

Since the pump so far described is generally similar to that shown in U.S. Patent No- 2,420,622, further detailed description of the generalfeatures thereof is believed unnecessary.

In accordance with the present invention, each of the pressure loadablebushing assemblies 13 and I5 includes an annular plate or insert 31 and38, respectively, these plates each having an outer diametersubstantially identical with the outer diameter of the flanged portionof the associated bushing but having an inner diameter slightly greaterthan the inner diameter of the hollow portion of the bushings in whichthe journals "la and Ho extend. In this manner there is provided by theannular plate 31 an annular chamber or relief recess which iscommunicated to a zone of low pressure through axially extending groove4| formed in bushing l3 and similarly an annular chamber or reliefrecess 42 is provided at the inner edge of plate 38 which iscommunicated to a zone of low pressure through axially extending groove43 in bushing 15. These chambers correspond in function and location,being located radially inwardly of the gear teeth of the associatedpumping gears, to the grooves ordinarily provided in the gear side faceengaging surfaces of the bushings of the pressure loaded pump, asdisclosed in the aforementioned patent. Since the outer diameter of thebody portion of the bushing assembly is fitted with a journal fit in thepumping chambers, making the outer diameter of the insert plates thesame as that of the flanged portions of the bushing assemblies ensuresconcentric location of the insert plates despite axial movement.

The plates 31 and 38 may be formed of any suitable wear-resistantmaterial and may be made of a metal, such as the metal of which thebushing itself is made, usually bronze, or may be made of other materialhaving a suitably low coefficient of friction such as synthetic rubber,nylon or various other similar materials. The axial thickness of theinsert must, of course, be suflicient to provide dimensional stabilityand this will vary somewhat with the material employed, the over-alllength of the flange bushing body portion being at the same time madegreater or less as the axial thickness of the plate is made less orgreater to provide the required end clearance.

In the operation of the pump; the inserts will be moved axially intosealing engagement with the gear side faces in response to applicationof discharge pressure to the motive surfaces 13a.

and l5a. After a period of use resulting in substantial wear of theinsert plates, the pump may be disassembled and the inserts replaced,thus materially increasing the useful life of the pump at relatively lowcost. The plates are, of course,

. free to move axially with respect to the pumping gears and are thusable to take up end clearance without distortion or deflection.

The size-of the relief recess or chamber which.

controls the effective sealing pressure may be varied withinconsiderable limits merely by changing the inner diameter of the twoinsertplates; this greatly increases the adaptability of a pump todifferent operating conditions. Also, the use of the plates facilitateseccentric location of the relief recesses as disclosed, for example,' inapplication Serial No. 168,587 of John A. Lauck, filed June 16, 1950.

Where herein the various parts of this invention have been referred toas being located in a right or a left position, or an upper or a lowerposition, it will be understood that this is done solely for the purposeof facilitating description and that such references relate only to therelative positions of the parts as shown in the accompanying drawings. I

While but one embodiment of this invention has been shown and described,it will be understood that many changes and modifications may be madetherein without departing from the spirit or scope of the invention]Also, while an important feature of the invention is the facility withwhich the relief groove may be formed, the

insert plates may be formed to fit closely the.

outer diameter of the gearjournal.

, bly also having a front face subject to the pressure in said pumpchamber and cooperable with the adjacent side face of said rotatablemember to provide a pumping seal therewith, said end plate assemblyincluding an annular disc-like member which can be moved axiallyindependently of said back face providing at one side thereof said frontface and having an inner dimension such that a relief recess is formedto limit the sealing area between said side face and said front face;means establishing communication between said relief recess and saidinlet and means establishing communication between said pressure chamberat the back face of said plate and said outlet, the relation of the areaof said back face to said sealing area being such that the force actingupon said back face of said end plate always exceeds slightly the forceacting upon said front face of said end plate whereby to maintain saidpumping seal without excessive friction, wear or lost volumetricefliciency.

2. A liquid pump comprising a housing having a pump chamber and an inletleading to and an outlet leading from said pump chamber, means includinga rotatable member received in said pump chamber for forcing liquid fromsaid inlet out of said housing through said outlet, an end plateassembly in said pump chamber having a back face normally spaced fromthe adjacent end wall of said pump chamber and having portionscooperable with said housing to provide a pressure chamber, said endplate assembly also having a front face subject to the pressure in saidpump chamber and cooperable with the adjacent side face of saidrotatable member to provide a pumping seal therewith, said end plateassembly including an annular disc-like member providing at one sidethereof said front face and having an inner dimension such that a reliefrecess is formed to limit the sealing area between said side face andsaid front face; said end plate assembly including said disc-like memberbeing axially movable in said pump chamber, said disc-like member beingreplaceable independently of the remainder of said end plate assembly,means establishing commnication between said relief recess and saidinlet and means establishing communication between said pressure chamberat the back face of said plate and said outlet, the relation of the areaof said back face to said sealing area being such that the force actingupon said back face of said end plate always exceeds slightly the forceacting upon said front face of said end plate whereby to maintain saidpumping seal without excessive friction, wear or lost volumetricefliciency.

3. In a fluid-pump of the type comprising a housing having a .pumpchamber formed therein application thereto of discharge pressuregenerated by said pump and to move said bushing toward said gear sideface, a substantially flat annular wear insert member interposed betweensaid forward surface of said bushing and said side face of said pumpinggear, said member having an outer diameter substantially equivalent tothe outer diameter of the forward surface of said bushing and having aninner diameter slightly greater than the diameter of said axiallyextending aperture, whereby to provide atsaid inner diameter a generallyannular relief recess, means placing said relief recess in communicationwith a zone of lower than discharge pressure, and means placing saidmotive surface in communication with discharge pressure generated bysaid pump.

4. In a fluid pump of the type comprising a housing having a pumpchamber formed therein and an inlet leading to and an outlet leadingfrom said pump chamber, pumping means including a pumping gear in saidchamber effective to force fluid from said inlet out of said housingthrough said outlet, a supporting shaft connected to said gear andhaving a portion extending axially from at least one side thereof, anaxially movable pressure loadable bushing associated with said gear andhaving an axially extending aperture formed therein to receive saidportion of said gear supporting shaft in journal relation, said bushinghaving a generally annular forward surface and an oppositely disposedmotive surface, said motive surface being effective upon applicationthereto of discharge pressure generated by said pump and to move saidbushing toward said gear side face, a substantially flat annular wearinsert member interposed between the said forward surface of saidbushing and said side face of said pumping gear, said wear insert membercomprising a material different from the remainder of said bushing andsaid gear, said wear insert member having an outer diametersubstantially equivalent to the outer diameter of the forward surface ofsaid bushing and having an inner diameter slightly greater than thediameter of said axially extending aperture, whereby to provide at saidinner diameter a generally annular relief recess, means placing saidrelief recess in communication with a zone of lower than dischargepressure, and means placing said motive surface'in communication withdischarge pressure generated by said pump.

ROBERT J. MINSHALL.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,879,136 Dubrovin Sept. 27, 1932 2,312,655 Lauck Mar. 2, 19432,312,891 Ferris Mar. 2,1943 2,420,622 Roth et a1 May 13, 1947 2,527,941Lauck et a1. Oct. 31, 1950

